The direct reduction iron-making method is developed as a method for manufacturing reduced iron by reducing iron oxide contained in an iron oxide-containing substance.
For industrial implementation of the above direct reduction iron-making method, there are a lot of issues that must be addressed, such as improvement in operation stability, economical efficiency, and reduced iron quality. The techniques of Patent Literatures 1 to 9 are proposed as an attempt to address such issues.
Among the above issues, improvement in the yield of reduced iron is particularly considered important in recent years. This is because, when the yield is poor, the costs rise and thus production in an industrial scale cannot be made. The techniques of Patent Literatures 10 and 11 are proposed as an attempt to improve the yield of reduced iron.
Patent Literature 10 (JP 2014-62321 A) discloses use of a carbonaceous reducing agent having an average particle diameter of 40 to 160 μm and containing 2 mass % or more of particles having a particle diameter of 400 μm or more.
As another attempt, Patent Literature 11 (U.S. Pat. No. 8,690,988), for example, discloses an agglomerate containing a first carbonaceous reducing agent having a size less than 48 mesh and a second carbonaceous reducing agent having a size between 3 to 48 mesh and having an average particle diameter larger than the average particle diameter of the first carbonaceous reducing agent. Herein, the first carbonaceous reducing agent is contained at 65% to 95% of the stoichiometric ratio that is needed for making the iron oxide-containing substance into reduced iron, and the second carbonaceous reducing agent is contained at 20% to 60% of the stoichiometric ratio that is needed for making the iron oxide-containing substance into reduced iron.